Analysis Of Thermal/Water Propulsion For Cubesats That Refuel In Space

Modeling is developed for a thermal water propulsion system for small spacecraft such as CubeSats and for larger spacecraft acting as their mother ship. Water is chosen as the propellant because it is easily mined on many planetary surfaces so that the spacecraft can refuel and continue their mission as long as they have an energy source. The propulsion system works by heating the water tank to high temperature and pressure, then venting the water vapor through a converging-diverging nozzle into vacuum. Modeling needed to account for the non-ideal gas behavior of steam while in saturated conditions of the tank and while expanding through the nozzle into space. The results show that a specific impulse of about 160 sec is possible, and that hopping distances for such spacecraft are in the range of multiple kilometers to tens of kilometers, depending on spacecraft mass, water tank size, and planetary gravity